In order to produce electricity from a wind turbine, the rotations of the wind turbine are typically transferred to an alternator, directly or through an intervening transmission system. Output power of the alternator is a result of the multiplication of the rotational speed of the wind turbine (in radians per second) by the torque (in Newton-meters) that is acting on a rotor of the alternator.
There is a trend to increase the span of wind turbines in order to capture more wind power; however, the rotational speed of the wind turbines has decreased. As a result, the torque induced by the wind turbine on the alternator rotor has increased accordingly. For example, for a 1 mega watt wind turbine rotating at 30 rpm (3.14 radians/second), the torque induced on the alternator rotor while producing 1 MW will be”
Torque=1,000,000 W/3.14 radians/second=318471 Newton-meter=32.5 metric tons. This enormous torque must be balanced by the construction of the wind turbine wherever it is placed, i.e., on the ground, offshore or in the air.